Which meaning from the dictionary best matches the underlined word as it is used in the paragraph?

my mother, a nurse, belongs to a group called angels at the ready. according to their constitution, members must be willing to travel. they must sign that they can go where needed any time of the day or night. it is hard on our family sometimes, but we are proud of her.

read the dictionary entry.

constitution (kahn-stuh-too-shun)
noun
1. the way something is put together
2. the physical nature of the body
3. the principles by which a group is governed
4. the document listing the principles by which a nation is governed
5. a custom

a.
1. the way something is put together

b.
2. the physical nature of the body

c.
3. the principles by which a group is governed

d.
4. the document listing the principles by which a nation is governed